Most likely is that you are asking demands of your engine to fulfill. The load on the engine to provide those loads does not seem to make the computers speed up the engine.
If, at idle, say your engine develops 5HP, able to keep itself rotating. Then you add air conditioning, now you need 6.5HP, so speed up please. Are the batteries down.. charge them.. 7HP. But the computer seems to want to slow, and not give more gas to match the load.
When I have A/C on and arrive at a stop light, I have to shut off A/C to keep up the RPM's so the clutch doesn't try to creep ahead and just lays calm.